eficaz
/efiˈkaθ/ · B2 · adj
effective
🎯 eficaz = effective: sounds like 'eff-ee-cass', hits the target every time
Eficaz comes from Latin efficax, from efficere, 'to accomplish, bring about'. English efficacy and efficacious share the same root, so the Spanish word is a close cousin. The -z becomes -c- in the plural: eficaces.